Injection of anhydrous ammonia into the soil is a commonly used method of supplying nitrogen fertilizer to grain and other crops using an applicator vehicle pulled by a tractor. An ammonia storage tank is pulled behind the applicator. A hose connects the storage tank to the distribution system on the applicator. The distribution system splits the ammonia into separate lines which feed multiple knives. These knives are lowered into the soil several inches and ammonia is injected into the ground at the bottom of the knives as the knives are pulled through the soil. It is normally desired that ammonia be applied uniformly over a field. One of the main problems is achieving this uniformity is difficulty in controlling a stream of mixed liquid and vaporous ammonia. Vaporous ammonia causes flow sensors to supply incorrect data and causes pump designs to become vapor locked. Cooling of the ammonia in a heat exchanger and pressurizing ammonia above its boiling point with a pump are methods of keeping liquid anhydrous ammonia below its saturation temperature.
The apparatus and method for providing vapor free liquid to an anhydrous ammonia flow control system, as described by U.S. Pat. No. 7,096,802 is a method of providing a liquid ammonia stream. This method separates the ammonia vapor from liquid ammonia in a tower with liquid level controlled valve. The method is analogous to a common stream trap which separates condensed water from a steam line. The commercial embodiment of the method described in U.S. Pat. No. 7,096,802 is the Liquimatic® vapor separator which has been in service since June, 2009. While it performed well in field operation, it was subject to occasional filter plugging. Also, there were some instances where entrained liquid anhydrous ammonia exited through the vapor exit lines on the separator.